Circum Brown Dwarf Disks Dissipate More Slowly

The number fraction of discs around brown dwarfs in Orion OB1a and the 25 Orionis group

Authors:

Downes et al

Abstract:

We present a study of 15 new brown dwarfs belonging to the ∼7 Myr old 25 Orionis group and Orion OB1a sub-association with spectral types between M6 and M9 and estimated masses between ∼0.07M⊙ and ∼0.01 M⊙. By comparing them through a Bayesian method with low mass stars (0.8≲ M/M⊙≲0.1) from previous works in the 25 Orionis group, we found statistically significant differences in the number fraction of classical T Tauri stars, weak T Tauri stars, class II, evolved discs and purely photospheric emitters at both sides of the sub-stellar mass limit. Particularly we found a fraction of 3.9+2.4−1.6 % low mass stars classified as CTTS and class II or evolved discs, against a fraction of 33.3+10.8−9.8 % in the sub-stellar mass domain. Our results support the suggested scenario in which the dissipation of discs is less efficient for decreasing mass of the central object.